Grid structure for cathode-ray tubes



Feb. 25, 1958 D. R. coNE 2,824,988

GRID STRUCTURE FOR cATHoDE-RAY TUBES Filed May 26, 1955 F16-2 n INVENToR.

5a/wm 2 Calvi BY Irma/lf3 Uflite States Patent O GRID STRUCTURE FOR CATHODE-RAY TUBES Donald R. Cone, Oakland, Calif., assigner to Chromatic Television Laboratories, Inc., New York, N. Y., a corporation of California Application May 26, 1955, Serial No. 511,150

S Claims. (Cl. 313-78) This invention relates to cathode-ray tubes especially adapted for color television image production. It is particularly related to an improved assembly and support for securing and supporting a color-control grid structure, or additional grid structures as well, within the tube envelope and in the tube wall. The support mechanism provides also for ready alinement of the supported grid structure relative to the phosphor-coated target element, whether that elementl be a separately supported target plate, er whether it be a phosphor coating applied directly to the inner surface of the tube face panel.

Various forms of color television tubes for producing images for direct viewing have been proposed in the art. Among the tube types which are proving to be particularly satisfactory is one utilizing a multiplicity of generally parallelly positioned substantially uniformly spaced linear conductors arranged in coplanar relationship to form a so-called color-control grid structure. The color-control grid structure is adapted for positioning substantially adjacent to a nal target upon which the color television image appears at times of excitation of the target surface by one or more impinging cathode-ray beams appropriately modulated under the control of video signal information.

This type of structure utilizes as a color-control grid a plurality of linear conductors of which, for the socalled single gun type of tube (that is, a tube in which a single cathode-ray beam only is projected from an electron gun to impact the target), adjacent linear conductors are maintained electrically insulated from each other and alternate conductors are electrically connected. For a tube of the type utilizing a plurality of cathode-ray beams to impact the target area, the various linear conductors of the color-control grid may all be electrically connected.

The tube type here being considered has provided on the target surface upon which the cathode-ray beam finally impinges after it is directed through and between the linear conductors of the color-control grid a seriesl of phosphor strips of different light producing characteristics. For tricolor operation, that is, where the iinal color television image is produced as an additive representation resulting from activation of phosphor strips to produce the image in three separate colors, the phosphor strips are formed to produce light, preferably in the colors red, green and blue. The phosphor strips are arranged according to a selected repeating pattern or color cycle. Illustratively, the phosphor strips may be of such characteristics as to produce light in color sequence of red, green, blue, green, red, green, etc., when the signal modulated cathode-ray beam is directed thereupon.

in the usual form of arrangement of a color television tube of this character, the phosphor strips to produce the dierent colors of light are so arranged that phosphor strips to produce one selected color of light, say, green, are electron-optically centered with respect to adjacent linearV conductors. All phosphor strips f V 2,824,988 Patented Feb. 25, 1958- f. ICC

this character also extend substantially parallel to the linear conductors of the color control grid. The phosphor strips to produce the light in the other two colors of the tricolor are, generally speaking, electron-optically centered beneath the linear conductors. Consequently, if the phosphor coating of the target is covered with a thin metallic film, such as an electrically conducting aluminum film, so that a high potential may be applied between this iilm and the electron source, and if the color-control grid is maintained at approximately the potential of the so-called G3 electrode (also frequently called the anode) of the electron gun, a strong electrostatic ield will be maintained between the color-control grid and the nal target and acceleration of the scanning cathode-ray beam will occur in the region between the color-control grid and the target. The eld also tends to refocus the electron beam directed from the electron gun to the color control grid, so that the beam is brought to a sharper spot at the plane of the phosphor-coated target. At times when the linear conductors of the color-control grid are all at the same potential with respect to each other, the cathode-ray beam directed to the target through the color-control grid will be focused at a sharply defined spot on that target strip which is electron-optically centered in the space between adjacent linear conductors through which the cathode-ray beam is directed. On the other hand, if one or the other of the linear conductors of the color-control grid is maintained at a higher potential (more positive) than the other, the electron beam passing adjacent thereto and between the linear conductors is not only accelerated toward the target but it is also deflected in the direction of the more positive voltage, in which case light is produced in a different color by what is known as a microdeflection of the scanning cathode-ray beam. l

The foregoing features are generally known in the art. Accordingly, it will be appreciated that this invention is not broadly directed to the control of the color image reproduction but, rather, is concerned particularly with the support of the color-control grid structure formed vof the plurality of linear conductors, each substantially uniformly spaced from the other, and all arranged substantially parallel to each other, and in coplanar relationship. It has been found in connection with a color-control grid of this character, that the support for the grid, since the linear conductors must all be kept taut if vibration and a resultant lack of color iidelity of the image is to be avoided, is frequently heavy and cumbersome, and adds considerably to the cost of manufacturing tubes, since the support for the linear conductors of the color-control grid usually is a rather heavy frame.

The present invention provides for the support of the linear conductors of the color-control grid directly in the tube wall, and thus provides for a cathode-ray tube construction in which the weight is greatly reduced, the structure greatly simplified, the opportunity to provide extremely tightly strung linear conductors, and oifers the opportunity of obtaining increased image area. Y At the same time there is no frame mass held or suspended tentials to adjacent linear conductors of the color controlV grid. The shielding problem is also simplified and can besupplied externally of the tube.

Therefore, included among the objects of the invention are those of providing greatly improved support struc- Other objects of ture forthe color-control grid, an improved tube'structure from theV standpoint of weight, a rigidityk Vof- Vthe color-control grid frame and its components, and a greatly simplified evacuation process. Y

Other-objects, of course, involve the production of a color'televisioncathode-ray tube offering increased oppor- VYtl'rnities yfor -large size images and an opportunity more readilyV to aline the-linear conductors of the color-control grid -with-the-phosphor coated strips upon whichrthe image is to-be realized v color-control grid, Y

.Referring now tothe drawings for a further understanding ofthe invention, thecathode-ray tube envelope of the type herein to` beA described comprises the usual flattened endi-wallthrough which the images are usually viewed, and thenzusually a funnel or conical-shaped portion merging into a .tubel neck, in which there is contained 4the sourcesto develop .the flow ofthe scanning cathode-ray beam or beams. These components are known in the art as theelectron; gun and comprise the source to release theelectrorlsl an appropriate control-for modulating electrode and one or more accelerating or anode electrodes Whichnare vcc'illectivclyrknown as the electron gunv (not shown). About the tube neck, and usually positioned at about the :point where the funnel or conical-shaped tube wall-merges ,with the neck, there may be positioned suitable deflecting coils for defiecting the developed cathode- Combinations of this sortare Ywell known, and are notV illustrated'herein forsake of convenience.

VAs the tubeY herein to be described Vis formed, it comprises aV face panel-11Y inthe form of a glass or trans-Y parent vitreous member through'which the produced im- Yage may be viewed from the directionV indicated Yby the arrowV external tothe tube.V LThe face panel isformed.- generally attened, and of aperipherry configuration which may-bel circular yor whichgmay closely approach rectangular. form,V depending, ofcourse, upon the type ofY tube manufactured. The inner surface of theface panel may, for some tubes, be coated with the .phosphor adapted to produce the image upon being excited and impacted by the scanning cathode-ray'beam, loi' the face panel may be left clear` and the image maybe produced upon a separate phosphor coated plate 15, as will later be described inrmore detail. The face panelof the present constructionis formed ingenerally dish-,shaped conliguration'with theflattened portion -17V providing the viewing area, and the -upturned portions 18 providing a more or less tubular sectionwhich-,isadapted to be secured to the funnel section ofthe tube envelope. Theifunnel section 19 of the tube likewise is provided for connection to the end of the tube and to be secureddirectly to or through tothe inter-V mediate components -to the upturned portion 18 of the face platell.V v

v*Theinvention herein to be described Yprovides partie` ularly for supporting and mounting a multiplicity of linear conductors of the character above described `so as tojpr'ovide the supporting frame work directly in the tube wall. To this end a multiplicity of parallelly strungilinear conductors or grid wires V21 are causedy to span the interior of the tube envelope and to extendfor approximately the distance across the ring-like upturned edgesV 18 of therface plate. Y usually formed ofiine wire of the order of about 3 mils, although ythis is not to be considered as a limiting statement, but rather illustrative, and-are spaced apart by-spac-V ings appropriate to-the size of the tubezand the image size to be developed. Illustratively, for a so-called 21V inch tube size and with the grid conductors spaced at approximately 700 mils from lthe phosphor coated target, the wire spacing may be of the order of 25 mils. All Vof the conductors 21 of the color-control grid are preferably held in `co-planar arrangement and extend as above stated,

` ray beam and causing it to sweep the target areaY of the tooverlap the upturned edges 18 ofthe face panel dish.'

Preferably, in the fabrication of the tube, the conductors are strung prior to tube assembly, so as to overlap a metallic ring-like memberZS, the surfaces -of which are ground at for Vready sealing and parallel to one or more suitable, plate mounting pins. The wires extend parallel to the mounting pins in the preferred construction.

Theiconguration of the ring-like member is such that it`also corresponds substantially to the periphery of the tube, and'it isof a cross section such that the plate extends slightly within the inner boundary of the upturnedf Y edgesl of thedish-like face panel and also slightly beyond.- the outer periphery thereof. After the grid conductors are appropriately spaced and tightly stretched across `the ring-like .member 23, they are caused to rest onY glassV frits 25 to separate them and insulate them from thefmetallic. ring-like member 23. Then, with the con-V ductors so stretched and resting upon theV glass-frits 25 other'glass ffrits 27 are placed thereover bled components; With the linear conductors of the colorcontrolgrid sostretched and so positioned, and the ringlikelmmbers 29 and 23 held closely together, the assembly is heated to the point where the glass Vfrits become g Y plastic andfimbed the-linear conductors and at the same' timeadhere to the surface of the linear conductorsandproducea bond withithe .metallic ring-like members 23 Y and 29. Thejglass frits haveVV a high melting Vtemperature by which- Vis meant that they melt at a'temperature higher thanany temperatureexperienced.inthe tube evacuation and bakeout. Consequently, when the linear. conductors ofthe color-control grid are passed through the glass fritsV andthe fritsrare'fused `to 4become a glass seal,.there is Y a bond Vformed between the adjacently positioned metallic ring-like members 23 and 29 and a grid support sandwich isfformed. At this ora later time the Vlinear lconductors of thev grid which protrude beyond the-sandwich edgeshown atj 31 cani be connected together if. desired,

or theQconnectionsmaybe establishedprior to the sealing operation.V vStr-sealed andso-formed, the sandwichy holds the linearconductors Iof thefcolor-control grid securely.

' the' funnelseotiomto ,fo-rm* the complete Vtube Wall `as-V there-maylor'may not'lbe a metal flange. 'The' secure- There hasbeen-establi'sheda bond between the wires and the support whichwillbel vacuum-tightl when'the tube is face Apanel andv4 the colori-controlgridY support sandwich,V

thereniay be secured al'ange 33 having a flattened surface of a form substantially matching that of themetallic ring-'like member ,29`of' the' color-control Vgrid support sandwich. Thetube may V'be provided as either. glass or metal bulbsh'for' instance, 'and where the bulb is glass mentfof the glass face panel. section to such aV metal ange.may"be ,accomplished inany desired fashion-as is As is well known, grid conductors of this sort are and a second r .metallic 'ring-like member 29 is rested upon the so assem- Well known in the art. When the flange has been secured, the face panel may then be supported against the metallic ring-like member 29 with suitable glass frits of lower melting temperature therebetween. When the components are heated, the glass frits are caused to become plastic, after which the heat is removed and, upon cooling, the glass frits form a glass seal between the flange 33 and the metallic ring-like member 29. Similarly, the funnelshaped section 19 of the tube, if formed of a metal, may have its outermost edge 35 also formed into a ilangelike element of a shape generally complementary to the ange 33. If the funnel-shaped section is of metal, it may be machined to provide the outer flange. This flange is then matched and rested against the ring-like iiange 23 of the color-grid support sandwich and by means of a bond provided by the glass frits shown at 37v may be secured to the color-control grid sandwich. Thus, the color-control grid sandwich when appropriately secured, as explained, to the upturned edges of the face panel and to the funnel section of the tube wall, forms a section of the tube Wall and is completely merged therewith. The conical or funnel-shaped tube wall then may be provided with a conducting coating 39 (in the case of the glass tube) for the application of suitable potentials thereupon. This coating is usually of a carbon type, such as that known as Aquadag The panel wall also has a very slightly conducting coating 4t) applied thereto. This latter coating may be in the form of an iron oxide (FeO) or a chrome oxide on the inside of thev face panel.

In the case of a tube of the sort in which the image is caused to appear on surface other than the face panel, a phosphor plate of the character illustratively shown at is provided within the tube. To this end there is formed within the tube wall and supported therein a plurality of support pins 41 and 42 to which is attached a suitable phosphor plate-supporting bracket in the form of a U-shaped element 43. Illustratively, the U-shaped element is arranged to extend at generally uniformly spaced locations with respect to the interior wall of the tube as formed by the upturned portion 18 of the face panel, so that if, for instance, the tube is of a sort such that the upturned section 1S follows a circular path, the U-shaped section 43 will also follow a circular path and extend throughout an arc of a circle suflicient to hold the edges of the phosphor plate 15 or the vU-shaped section may be short length sections so that the phosphor plate edges may be held at spaced locations. Where the tube is formed to provide a viewing area more closely rectangular in shape than the U-shaped brackets, it may conform more closely to one side of a rectangle. The phosphor plate 15 is then positioned within the bracket prior to the assembly of the color-control grid with the upturned edges of the face panel. The connection shown by -,the conductor 47 extending through the tube wall is to'provide high voltage which may be connected at the terminal point 48. The plate 15 .so formed is coated with phosphor adapted to iiuoresce or become luminescent to electron beam excitation as above explained. The phosphor is coated with aluminum or other suitable metallic lilm conventionally represented at 49, and high voltage is applied to the hlm. As is well known, the electron beam. from the electron gun which has been diagrammatically shown in the figure by the dot-dash line passes adjacent to and between the conductors of the colorcontrol grid to impact the phosphor-coated plate 15 of the face panel, as likewise explained. For the purpose of providing voltage on the conductors of the colorcontrol grid, the adjacent wires are maintained electrically insulated from one another by the seal formed by the fusion of the glass frits. Alternate conductors of the color-control grid are electrically connected. Appropriate potentials may be applied to these conductors and there may then be superimposed upon this steady potential an oscillatory potential to cause the scanning cathoderay beam to oscillate in its inotionalV path so that it is caused to impinge upon the phosphorsto produce light in the different colors in controlled manner. Oscillations of the scanning cathode-ray beam for conditions where colored images are produced according to standards established at present in the United States by the Federal Communications Commission may use an oscillation of the order of 3.58 megacycles per second, which oscillation is then provided by the connection of the high frequency coil shown at 53 to which the oscillatory voltage from any appropriate source, not shown, is applied. A shielding housing 55 is secured to the outer edge of the support sandwich for the color-control grid and surrounds the coil 53 electrically to shield the oscillations from having an external effect.

The foregoing description, particularly for purposes of simplified explanation, treats the invention and its specific embodiment in the nature of a color-control grid structure of a sort wherein the separate linear conductors are parallelly positioned with respect to each other and are all arranged in substantially coplanar fashion with respect to each other. However, as is known in the art, it is advantageous in some tube types to have the linear condoctors of the color-control grid maintained in parallel relationship to one another but, in addition, located along a generally cylindrical path at readily determinable distances from one or more points in space. This form of grid does not permit of a strictly coplanar relationship of the linear conductors with respect to each other. Grid structure of the sort last mentioned are known in the art as cylindrical grids and are particularly useful in tube types where a high degree of correction of the sort known in the art is desired and Where the angle of deection of the cathode-ray beam is very large. It will be apparent that the construction herein shown for providing the sandwich within which the linear conductors of the color-control grid are held may readily be of such peripheral shape and configuration as to provide for holding the cylindrical type color-control grid structure as well as the planar type color-control grid structure.

In addition, for purposes of simplified explanation, it has been particularly indicated herein for description purposes that the phosphor coating on the impacted target area shall be upon the plate 15, but, as is hereinabove noted, it is frequently desirable for direct viewing and in some type of tube envelopes that the inner surface of the face panel 11 shall be coated with phosphors and that the resultant image shall appear to the viewer directly upon the inner surface of the face panel which is viewed. In this event, plate 15 and its coating may be omitted and the phosphor coating and the associated conducting metal lm will then be placed upon and supported upon the inner surface of the face plate forming the end of the tube envelope. It is, therefore, intended that in vthe denition of the invention as presented in the claims hereinafter appended the construction shall be broadly interpreted unless otherwise limited by specific claim terminology. v

From the foregoing it will be apparent that the socalled sandwich to support the grid wires is positioned slightly closer to the source of the electron beam or cathode-ray beam than is the target area upon which the images are to appear. Consequently, it will be borne in mind that the internal opening provided in the ringlike members 23 and 29 may be slightly less than the area of the image which is to be developed at the target, due, of course, to the angle at which the electron flow from the tube electron gun structure is directed toward the target. Alternatively, the area may be equal to the target area on which the image is to appear, or, if desired, it could be slightly larger. Accordingly, in the claims, reference to the relative dimensions of the central opening in the rings with respect to the target area when dened as approximately the same will be understood in accordance with this description.

1 Having now described the invention, what is-claimed is:

717; A,YcatliodefrayY tube Yfor-color television comprising a gridjsupportframeconsisting of a pair of support rings each having a central-opening ofarea and configuration generally correspondingto Vthatof an image Yto be produced withinthetube Vforviewing, a multiplicity of tautly strungrprarallellyV positioned linear conductors overlapping .Opposite edges of theV support ringsrand located therebetween, a glass seal between the supportV rings imbedding Vthe overlapping linear conductors and servingvr for sealing VYthe support rings toieach other in sandwich fashion and forY anchoring the tautly strung conductors between the Ysupport rings in sandwich fashion, a face panel and a .Y vfunnel section, means to seal. and secure the face kpanel to one outer surface of the sandwich supporting the linear Yconductors and means'to seal the funnel section to the opposite outer surface of the sandwich supporting the Y linear Yconductors to provide a Vtube wall section which will be vacuum-tight upon tube exhaust. Y

' 2'. A lcathode-ray tube for. color television comprising a grid support'frame consisting of a pair of support rings eachk having a centralV opening of area and coniiguration generally corresponding to that of an image to be prolduced within the tubefforviewing, a multiplicity of Vtautly strung parallelly positioned coplanarly arranged linear conductors overlapping opposite edges of the support rings Vand located therebetween, a glass seal between'the support rings imbedding the overlapping linear conductors Vand'serving for sealing the support rings to each other in sandwich'fashion and for anchoring the Ytautly strung conductors between'the .support ringsfin sandwich fashion, a face panel and a funnel section, means to seal and secure the face panelv to one outer surface of thel sandwich supporting the linearconductors and means to seal the funnel section to the oppositerouter'surface of the sandwich supporting the linearconductors to provide a tube wall section which Vwill be vacuum-tight upon tube exhaust. Y 3. Acathode-ray tube for color television including a face panel, a funnel section adaptedfor securement tol the face panel about its peripheral edge, a color-grid supsealing means having a melting pointV higher than the-V` temperature produced during evacuation and bake-out of the, tube for securing the support rings andranchoring the linear conductors between the said supportringsin port frame comprising a pair Vof support rings, a multiplicity of [substantially uniformly spaced and tautly held substantially parallelly positioned linear conductors overlapping opposite edges of the support rings and frit means v having a melting point higher than any temperature producedduring evacuation and bake-out of the tube held between the support rings and adapted upon heatingrto aplastic 'state to' imbed the voverlapped linear conductorsV and to adhere to the rings and the conductors and subsequently` when cooled to a solidV state to secure and seal Y' the support rings to each other Vin vacuum-tight manner Vand to anchor the grid Wires between the support rings in sandwich fashion, and glass Vfrit means for securing the face panel and the funnel section of the tube components to the outerY surfaces of the color grid support sandwich.

4. The tube claimed in claim 3 comprising, in addition,

`means to establish electrical connection to the color-grid linearconductors sealed between the sandwiched ring-like members, means to connect electrically therconductors of* the color-grid so that alternate conductors are electrically connected and adjacent conductors electrically insulated '.from eachother to formV the grid conductorsinto two electrically separate sets, means to introduce high frequency Voscillations between'` adjacent vconductors and shielding means surrounding the meansto provide high frequency oscillations;

5. Thetube claimed in claim l3 comprising, in addition,

. a flat ground metal ring secured to the edge of the dishlile face panel, a second flattened metallic ring secured to the edge'of'thefunnel member and glassffrit means to secure theY metal `rings tothe metal rings of the gridV conductor support sandwich.

6; A cathode-ray tube for7 color television including a sandwich fashion and glass sealing means for'securing the Vface panel and the funnel section of the tube'components Y. to opposite outer surfaces of the linear conductor supportl and anchoring sandwich.

7. A cathode-ray tube for color televisioncomprisingY a face plate section of dish-like formationV having aV gen-` i Y erally flattened window area and .upturned edges section-V ally forming a ring-like pattern, a Vfunnelrshaped bulbou's e portion for the tube also having a ring-like cross section Y of substantially like vform and adapted for securement with Y the dish-like face panel, a gridV conductor support sandwichicomprising a pair of flattenedring-like membersof peripheraliconfigurationsubstantially Ycorrespondingrto thej ring-like formation ofthe funnel and face plate sections, a multiplicity of tautly strung grid conductors and gener.- ally uniformly spaced in parallel relationship to eachother and located between the flattened ring-like members, glass Y sealing means'sandwiched between the attenedringllike members between which the grid conductors. are passedV and which-sealing means upon beingheated to a plasticA state ows around the conductors and which, upon .coole ing, `solidiies vand forms a bond between the ring-like Vmembers and an anchor for Securing they tautly strung grid conductors between the frame sections, the said Yglass seal having a melting `point higher lthan any temperature produced during tube evacuation andbake-out, and'. glass sealing means for securing the face panel andthe funnel section to the outersurfaces of the ring-like sandwiched Y support members. Y

8. A cathode-ray tube for color television comprisnga Y face plate section of dish-like formation having a generally flattened window area and upturned edges sectionally I forming a ring-like pattern, a funnel V'shaped bulbous pory tion for'the tube also having a ring-like cross section of substantially like form and adaptedfor securement with the dish-like face panel, a grid conductor support sand'- wich comprising a pair of attened ring-like members of peripheral coniguration substantially corresponding'to'the ring-like formation of the funnel and face plate sections,

a multiplicity of tautly strung grid conductors arrangedin l coplanar array and generally uniformly spaced in parallel relationship to each other'and locatedbetween the ilat-l tened ring-like members, glass'sealingm'eans Asandwiched between the attened ring-like. members between whichv the grid conductors are passed and whichV Vsealing means i upon being heated t'o a plastic Vstate flows around the con# ductors. and which, upon cooling, solidies and forms ar bond between the ring-like ymembers and an anchorfor securing the tautly strung grid Yconductorsbetween the frame sections, the said glassseal having a meltingpoint Y higher than any temperature produced during tube evacu-v ation and bake-out, and glass sealing means for securingV the face-panel and the funnel section Vto theY outer' surfaces ofthe ring-like sandwiched supportmembers. Y Y Y i References Cited in theg tile of this patent` Y. I i i UNITED STATES PATENTS y Beckers Dec. 1,l 1`95 Zaphiropoulos Feb;28,195.6 

